The purpose of the project is to elucidate the interaction of biomaterials used for specific implants with the physiological environment and to explore specially prepared biomaterials and design features with respect to their suitability and performance in a variety of contexts. For catheters designed to be used in the vascular system, thrombogenic events have been reduced by incorporating an anticoagulent at various levels within hydrogel layers which are attached to the surface. Slow release of the anticoagulant has significantly reduced the amount of clot generated on the surfaces as compared with untreated polyurethane catheters. Specific hydrogel formulations have been shown to reduce drag and eliminate sticking of catheters in the vascular system. A multi-lumen micro-catheter which is propelled and directed through small diameter blood vessels via jets of fluid emanating from its distal end has shown promise for negotiating heretofore difficult to reach areas. The catheter is controlled by an adjustable pressurized manifold operated by a joy stick. A transparent model of the vascular network simulating blood flow of a pulsatile nature was designed to evaluate the efficiency of the jet catheter system and its behavior in administering embolizing agents and chemotheropeutic drugs. Ex vivo studies of the polyurethane insulation of stimulating and pacing electrodes, along with long-term in vitro coupon studies have indicated reliable stability for segmented polyurethane for a number of surgical applications. Good correlation exists between in vivo and in vitro data for ultimate tensile strength and elongation over short-and long terms. Minor changes in physical properties when stored wet appear to be the result of a plasticizing effect which is reversible on drying. Segmented polyurethane stored in water with high bacteria counts over a 13 year period show up to 30% decrease in strength although the same material implanted in a sterile subcutaneous pocket for 3 years showed no appreciable changes. Our studies and that of others confirm that particles shed from the surfaces of in vivo and in vitro devices are not totally avoidable but can be minimized by careful control of the materials used for catheters, heart assist devices, injection sets, etc.